1. Field of the Invention
The present invention relates to a technique of heating a target material, such as shredded resin components of used automobiles, up to a softening temperature to remove a film from a substrate thereof, and recyclably sorting the substrate which has succeeded in removing the film therefrom.
2. Description of the Related Art
Heretofore, great efforts have been made for recycling resin components of used automobiles, such as resin bumpers. In the recycling process, if the resin component is coated with a film, the film is likely to be not fully removed and left on a substrate. Consequently, a component made of a recycled material from such coated resin products has a problem about mechanical properties, such as occurrence of cracks in a portion having a residual film due to external force applied thereto, and/or a problem about deterioration in appearance.
Thus, there is the need for forming a recycled product using only a resin free of a residual film.
As one example of a technique of recycling such a coated resin product, Japanese Patent Laid-Open Publication No. 2001-353721 discloses a technique of shredding coated resin components into fragments, pre-heating the fragments up to a temperature just before a melting temperature thereof, agitating the pre-heated fragments in a treatment vessel, and rapidly increasing the temperature of the fragments under agitation at the start of the agitation to reduce a process time.
Generally, in a coated resin product, a film (typically, thermosetting resin) and a substrate (typically, thermoplastic resin) are different in melting point from each other, and plural types of resins different in melting point, as typified by ABS (acrylonitrile butadiene styrene) and PC (polycarbonate), are used for a resin molding process. Moreover, temperature characteristics of a resin material are varied depending on the types (talc, glass, calcium carbonate, etc.) and contents of additives to be contained in the resin material. For example, as shown in FIGS. 10A to 10D, a heat deflection temperature of a resin material, i.e., a temperature at which a resin material exhibits a certain deformation (the resin material is softened in a non-molten state) during heating at a constant speed under a constant load, is changed to some extent depending on the types and contents of additives or resin matrix compositions. Thus, in a recycling process for a mixture of plural types of resin products, if the mixture is simple heated up to a single softening temperature, a part of the resin products which have not being softened to have residual films will be undesirably mixed with the resin products which have succeeded in being soften to allow films to be removed therefrom.